HTML no longer parsed in tooltip formatter

[Bilge]

Bug report

Codepen

https://codepen.io/bilge-the-encoder/pen/YzpqLPo

Explanation

In previous versions, HTML was processed as HTML. Now, it appears to be escaped and thus printed literally. This is a breaking change and not desired. Broken since 3.24.0.

[junedchhipa]

Duplicate of #2202

[junedchhipa]

Re-opening this due to Cross-site Scripting (XSS) - DOM vulnerability